ス-パ-オキシドジスムタ-ゼの化学--Cu,Zn-SODの構造と機能 (「生体関連微量金属をめぐる最近の話題」特集号)

概要

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Superoxide dismutases, SOD, are enzymes which catalyze the dismutation of superoxide, O-2, and contain iron, manganese or copper-zinc in the active sites. The iron-and manganese-containing SODs occur mainly in prokaryotes and the copper, zinc-SOD in eukaryotes. The primary structure of the enzymes have been determined in the Mn-SODs from E. coli and B. stearothermophilus and in the Cu, Zn-SODs from human and bovine erythrocytes and from baker's yeast. The molecular structural data are available only for the bovine enzyme. The enzyme consists of two identical subunits, each of which contains one Cu (II) and one Zn (II) bridged by an imidazolate anion from the side chain of histidine. The Cu (II) ion is coordinated to four histidine imidazoles and the Zn (II) to three imidazoles and one carboxylate of aspartic acid. The Cu (II) -bridged imidazole bond is dissociated upon reduction of the enzyme. The structure and function of the Cu, Zn-SOD are reviewed from the chemical view-points.
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